In the production of hydrogen, it is well known in the art to treat hydrocarbon material with a catalyst at high temperatures in the presence of steam. The hydrocarbon materials generally used are natural gas and naphtha which have been desulfurized to 0.1 part per million (ppm, by weight) sulfur. Hydrogen, carbon monoxide and carbon dioxide are the products of the reaction. These products are often cooled and passed over a shift conversion catalyst where the carbon monoxide is further reacted with steam to produce additional hydrogen and carbon dioxide.
Hydrogen generators and especially hydrogen generators for fuel cell powerplants may be required to operate with heavier fuels and, in the future, coal derived liquids. These heavier distillate fuels cannot readily be desulfurized to the 0.1 ppm sulfur level that is required for the conventional steam reforming process. Direct reforming of heavier fuels without desulfurization require higher temperatures to overcome the reduction in catalytic activity in the presence of sulfur. When the commercially available nickel steam reforming catalysts are used in this fashion, carbon deposition and reactor plugging occur and reactor operation cannot be sustained. The problem of carbon formation with conventional nickel catalysts can be overcome by adding air or oxygen to the hydrocarbon/steam fuel mixture. At oxygen to carbon ratios (O.sub.2 /C) equal to or greater than 0.42-0.46 carbon formation is eliminated with a 1360.degree. F. (738.degree. C.) preheat. In order to maximize the hydrogen production it is desirable to lower the oxygen to carbon ratio below 0.42. For example, for fuel cell powerplant applications, O.sub.2 /C in the range of 0.35 are desirable.
In general, conventional autothermal reformers utilize high activity nickel reforming catalysts containing 15-25% nickel on .alpha.-alumina or magnesia doped alumina. However, in use, the nickel-reforming catalysts are subject to carbon plugging if the oxygen to carbon ratio falls below a critical level (note the partial oxidation reaction above). As would be expected, the oxygen to carbon ratio required for efficient operation of an autothermal reformer would be lower than the critical oxygen to carbon ratio necessary to prevent carbon plugging of the nickel reforming catalyst in this environment. For example, for autothermal reactor operation, oxygen to carbon ratios of 0.35 or less are required, whereas typical critical oxygen to carbon ratios for such a reactor are 0.42 to 0.46 at a 1360.degree. F. (738.degree. C.) reactant preheat temperature.
Accordingly, what is needed in this art is a reforming catalyst particularly adapted to use in an autothermal reformer which is less sensitive to oxygen level and specifically less sensitive to carbon plugging because of critical oxygen to carbon ratios.